Numerical Study on the Influence of Coal Ash Particle Concentration and Particle Size in Flue Gas on Heat Transfer of Fire Tube Waste Heat Boiler

In order to study the influence of ash particle concentration and particle size in flue gas on the heat transfer performance of waste heat boiler, the Euler-Lagrange method was used to simulate the gas-solid two-phase flow and heat transfer in the heat exchange tube of waste heat boiler. The results indicate that: in a certain concentration range, the average heat transfer coefficient of heat exchange tube wall increases with the increase of particle concentration. The deposition rate of coal ash particles on the wall of the heat exchange tube is approximately linearly related to the concentration of coal ash particles. When the concentration of coal ash particles is high, the larger the particle size, the greater the impact on heat transfer. Particle size 30 μm and 35 μm the coal ash particles are prone to deposition on the pipe wall. Particle size between 5-30 μm the sedimentation rate of particles within the range of will increase with the increase of particle size. The particle size of coal ash particles is 5 μm, the performance of the heat exchange tube is optimal. The radiation heat transfer caused by the increase in the concentration of coal ash particles is greater than the convective heat transfer caused by their disturbance to the flue gas. The influence of particles on heat transfer in the heat exchange tube is mainly due to the radiation effect of particles.